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CHAPTER I. Introduction and background

Figure I.1 The two common ways of representing 5f-orbitals: the cubic set, and the general set. 3

Figure I.2 Accessible oxidation states for the actinides. 4

Figure I.3 Variation of the ionization enthalpy (IE) with the atomic number for A. lanthanides B.

actinides.

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Figure I.4 Schematic energies of actinyl valence orbitals. 12

Figure I.5 Gas-phase synthesis of uranyl ion, UO22+, by ion-molecule reactions of U²⁺ with 1.

Molecular oxygen, 2. Carbon dioxide, 3. Nitrous oxide.

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Figure I.6 Valence spinor energies (eV) as a function of bending angle (degrees) for ThO2, PaO2+

and UO22+ from relativistic calculations at M-O = 1.9 Å.

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Figure I.7 Basic diagram of mass spectrometry: generation of ions from compounds in sample, introduction into the ion source, separation by their m/z ratio and detection.

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Figure I.8 A schematic representation of the possible pathways for ion formation from a charged liquid droplet.

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Figure I.9 A schematic representation of the ESI-ion source. 24 Figure I.10 A. Basic components of a TOF mass analysis system featuring an ion mirror, and the

means by which it achieves m/z-based ion separation. B. Basic components of a magnetic sector mass analyzer system; C. Scheme of a cubic analyzer cell. The cyclotron motion and the excitation process is shown schematically. D. Orbitrap mass analyzer.

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Figure I.11 Schematic representation of a quadrupole ion trap. 31

Figure I.12 ICR ion trap configurations. E=excitation; D=detection; T=end cap (“trapping”). (a) cubic; (b) cylindrical; (c) end caps segmented to linearize excitation potential (“infinity”

trap); (d) and (e) open-ended; (f) dual; and (g) “matrix-shimmed”.

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Figure I.13 Ion cyclotron motion. 34

Figure I.14 An rf burst accelerates the ions, generating a transient ion image current signal (left).

The signal is digitalized, stored in the computer and a Fourier transform is applied to the data to convert the information into a mass spectrum (right).

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Figure I.15 Schematic representation of the three natural motions of an ion confined in an ICR cell (m-magnetron rotation; c-cyclotron rotation; T-trapping oscillation).

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Figure I.16 FT-ICR-MS sequence showing the order of the different time-separated process steps. 36 Figure I.17 Schematic representation of the operation of FT-ICR-MS. 36 Figure I.18 Potential energy diagram for a substitution reaction in the gas phase and in solution

in water.

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Figure II.1.1 Pseudo-first order kinetics plot for the reaction of UO22+ with CH318O. 79 Figure II.1.2 Potential energy profiles for the oxo-exchange reactions of UO2+ with water (red) and

methanol (blue).

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Figure II.1.3 Structures of the species found in the potential energy profiles for oxo-exchange between UO2+ and methanol (top) or water (bottom).

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Figure II.1.4 Section of the potential energy profiles for the oxo-exchange reactions of UO22+ with water (red) and methanol (blue).

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Figure II.1.5 Calculated Laplacian of the electron density at the An-O bond critical points obtained from with the Atoms in Molecules approach.

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Supporting Information

Figure S1. Structures of the species 2, 3 and 5 on the potential energy profile for the reactions of UO2+ with methanol (top) and water (bottom).

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Figure S2. Calculated Laplacian of the electron density at the An-O bond critical points obtained from with the Atoms in Molecules approach.

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II.2 Gas-phase uranyl, neptunyl and plutonyl: Hydration and oxidation

Figure II.2.1 Top spectra: Products of isolated (a) U^VO2+, (b) Np^VO2+ and (c) Pu^VO2+ after a reaction time of 10 s.

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Figure II.2.2 (a) Geometric structures of pentahydrated AnO2+ ions. AnO2+·(H2O)4(H2O) is the ground-state structure, whereas AnO2+·(H2O)5 is higher in energy. (b) Lowest-energy optimized structures of tetrahydrated AnO2OH⁺ ions.

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Figure II.2.3 Top spectra: Reaction of isolated UO2+ for 5 s: (a) with background gases; (b) after addition of air to the ion trap. Bottom spectra: Reaction of isolated UO2+∙(H2O) and UO2(OH)⁺ with background gases and added air for (c) no applied reaction time; and (d) a reaction time of 0.5 s. The product spectrum (d) shows O2-addition to UO2+∙(H2O)2

and UO2+∙(H2O)3, but not to UO2+∙(H2O).

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Figure II.2.4. Lowest-energy optimized structures for UO2+(O2)(H2O)n, n = 03. All the species are in the doublet ground spin state.

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Figure II.2.5 Lowest-energy optimized structures for NpO2+(O2)(H2O)n, n = 03, in the (open-shell) singlet ground spin state and in the quintet spin state (in parenthesis).

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Supporting Information

Figure S1 Ground-state and lowest-energy isomers of UO2(OH)⁺·(H2O)4. 143 Figure S2 Ground-state and lowest-energy isomers of NpO2(OH)+•(H2O)4. 143 Figure S3 Ground-state and lowest-energy isomers of PuO2(OH)⁺·(H2O)4. 144

xxxi Figure S4 Representative kinetics plot for hydration of UO2 (m/z 270) showing linear

logarithmic decay of the reactant ion, and in-growth of the primary hydrate, sequential hydrates and the O2-addition product.

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Figure S5 Addition of oxygen to U^VO2+.(H2O)n hydrates: (a) no air with no applied reaction time and (b) added air with 1 s reaction time.

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Figure II.3.1 ESI mass spectrum of a 10^-4 M water solution of UO2Cl2. 154 Figure II.3.2 Mass spectra for different reaction times showing O2-addition to isolated [UO235Cl2]^-. 157 Figure II.3.3 Plot of the rates of O2 addition to [UO2X2]^- ions (k from Table II.3. 1) as a function of

II.4 Exploring the nature of actinide polysulfide ions

Figure II.4.1 Mass spectrum from the reaction ThS²⁺ + COS. 184

Figure II.4.2 Computed structures of (a) GS US22+, (b) US22+ thiouranyl isomer, (c) GS US2+ and (d)

GS US2. 192

Figure II.4.3 Computed GS structures of US32+ and US42+. 192

Figure II.4.4 Computed DFT (TZP/B3LYP) ground state structures of ThS2, ThS3 and ThS4 neutral,

monocation and dication. 193

Figure II.4.5 Computed DFT (TZP/B3LYP) ground state structures of ThOS, ThOS2 neutral,

monocation and dication. 193

CHAPTER III. Lanthanide and actinide cluster fragmentation and chemistry

Figure III.1 1. CID mass spectra for isolated CaSr(NO3)5-, CaBa(NO3)5- and BaSr(NO3)5-. 215

xxxii Figure S15. Computed Lu(UO2)Cl6- ground state (GS) and higher energy isomers. 238 Figure S16. Computed ground state La(UO2)Cl6- and Lu(UO2)Cl6- possible fragmentation products. 238 Figure S17. Computed ground state MgLuF6- ,La(UO2)F6- and Lu(UO2)F6-. 239

xxxiii CHAPTER IV. Coordination of actinyl ions with amino acids in the gas phase

Figure IV.1 Representation of an amino acid which contains both acidic (carboxylic acid fragment) and basic (amine fragment) centres.

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Figure IV.2 Solid state interactions between uranyl and imidazole or imidazolium: direct coordination and H-bonding to oxo ligands.

Figure IV.7 CID mass spectrum of [UO2(Cys-H)(Cys)2]⁺ with lower (top) and higher (bottom) energy of fragmentation.

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Figure IV.8 CID spectra of [Ca(Cys-H)(Cys)2]⁺ (top) and CID of [Ca(Cys-H)(Cys)]⁺ (bottom). 313 Figure IV.9 Suggested structures for the neutrals Cys*and Cys& and the observed fragments

–HOOCCHCH2 and –Cys-S. Figure IV.14 Competitive CID spectra of positive uranyl mixed-aa species. 329 Figure IV.15 CID of positive uranyl mixed ligands: A. [UO2(His-H)2(Asp-H)]^- B. [UO2(His-H)2(Cys-H)]

-C. [UO2(His-H)(Asp-H)2]^-.

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Figure IV.16 CID spectra of Pu(VI) mixed species in the negative mode. 334 Figure IV.17 CID spectrum of Pu(V) mixed species in the negative mode. 334

Figure S1 ESI-MS spectra of uranyl chloride + amino acid solution (1:4) in the positive mode. 343 Figure S2 ESI-MS spectra of uranyl chloride + amino acid solution (1:4) in the negative mode. 343

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